Diamond is an important luxury and industrial material which nature provides and also now can be made synthetically. Whether it is natural or synthetic, diamond is actually a family of materials, and some forms of diamond are more useful than other forms for particular applications as the properties of the different forms vary. Types of diamond known in the art include, for example, microcrystalline diamond (MCD), nanocrystalline diamond (UNCD), and ultrananocrystalline diamond (UNCD). Diamond can comprise a plurality of individual grains of diamond, and the size of the grains can vary. In many cases, it is desirable to control the form or the morphology of the diamond down to smaller and smaller scales, including down to the nanoscale, so as to obtain the best properties. Diamond can be an expensive material, and the cost of different diamond forms can vary. Hence, for commercialization, it is important to better understand how to synthesize diamond with better properties and cost-benefits under commercially realistic conditions. For example, one important commercial application is in the area of MEMs and components such as scanning probe microscopes and atomic force microscopes which require use of hard, durable tips. See, for example, Synthesis, Properties, and Applications of Ultrananocrystalline Diamond, 2005; Handbook of Industrial Diamonds and Diamond Films, 1998.
One method to make diamond is chemical vapor deposition (CVD). In this method, a chemical vapor can be reacted over a solid surface, and the result is the formation or deposition of a material on the solid surface. For example, one can react in a CVD reaction chamber multiple components including for example (i) a compound comprising carbon with (ii) hydrogen gas to form diamond on a solid surface. Or one can react a compound comprising carbon in the presence of a noble gas to form diamond on a solid surface. One can use a hot surface or plasmas to activate reaction. In recent years, much interest has arisen in use of noble gases in the diamond deposition because the type of diamond made from these processes, sometimes called ultrananocrystalline diamond (UNCD), can provide advantages including very smooth as-deposited surfaces, high hardness, have small particle grain sizes, low deposition temperatures, the ability to pattern to nanoscale resolution including use of self-aligned deposition, and other useful properties. Useful properties can be, for example, mechanical, tribological, transport, electrochemical, or electron emission in nature. See, for example, U.S. Pat. No. 7,128,889 (Carlisle et al.) and U.S. Pat. No. 5,849,079 and publication no. 2005/0031785 (Carlisle et al).
However, while CVD can be a successful method for research in diamond science, commercial production can provide demands which are not addressed by academic research. For example, in commercial fabrication, one may need to form the diamond in a shape such as a sharp tip, for example. Therefore, despite these advances, a need exists to develop methods of synthetic diamond production for commercial applications, including UNCD production, which are more amenable to, for example, deposition into shaped surfaces, deposition over larger surface areas, use of multiple substrates and shaped surfaces, faster deposition rates, deposition with good uniformity, and deposition at lower temperatures.